The document discusses optical fiber communication and related topics. It describes the key processes involved which include generation, modulation, transmission, amplification and reception. It also discusses the different types of optical fibers used, how light is absorbed and emitted, population inversion necessary for stimulated emission, layers surrounding fiber cables, materials used to manufacture fibers, and applications of optical fibers such as delay lines, sensors and endoscopes.

1. Semiconductor Physics
OPTICAL FIBER COMMUNICATION
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2. Processes involved
 Generation
 Modulation
 Transmission
 Amplification
 Reception by photo detectors
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3. General communication System
Information Transmitter Transmission Receiver
Source (Modulated) medium (Demodulator)
Destination
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4. Types of optical fibers
 Step-index single mode fiber
 Step-index multi mode fiber
 Graded index multi mode fiber
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5. Absorption & Emission of
radiation
 Absorption
 Spontaneous emission
 Stimulated emission
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6. Diagrammatic representation
E2
hv= E2-E1
E1
Absorption
E2
hv= E2-E1
E1
Spontaneous Emission
E2
hv= E2-E1
E1
Stimulated Emission
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7. Population Inversion
 Necessary condition for stimulated emission
 Process of accumulation of e- at E2 level and
vacuum states at E1 level
 Required to:
 Enhance radioactive recombination
 To move fermi level into CB & VB.
 To cause accumulation of e- in CB & VB
 Responsible for laser action
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8. Layers surrounding Fiber
cables
 Primary coating
 Gives additional mechanical strength
 Protects fiber from stress
 Protection against chemical attacks
 Buffer jacket
 Avoids the formation of microbends
 Bending stress is relieved
 Fiber losses are reduced
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9. Layers surrounding Fiber
cables…
 Outer Jacket
 To reduce abrasion and to provide extra
protection against external mechanical strength
 Filler materials
 To avoid moisture absorption by fibers
 Prevents corrosion
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10. Layers of Fiber cables
Jacket
400 µm
Buffer
250 µm
Cladding
125µm
Core
8µm
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11. 1. Single Fiber cable
 Fiber is made from brittle glass
 Buffer jackets made of plastic
 Silicon coating between buffer jacket and
optical fiber
 Final cover by black polyurethane
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12. 2. Multi fiber Cable
 Used in telecommunication
 Kevlar is used to provide tensile strength
 Outer sheath for protection against impact
forces (forces generated due to brittleness)
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13. Advantages of optical fiber
as waveguides
 Wider band-width
 Low transmission loss
 Signal security
 Small size & weight
 Flexibility
 Easy maintenance
 Low cost
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14. Materials used to
manufacture optical fibers
 Glass fibers
 Crystalline and fluoride fibers
 Plastic clad glass fibers
 Plastic fibers
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15. Application of optical
fibers
 Fiber optic delay lines
 By using low loss optical fibers
 Fiber optic sensors
 By utilizing external influences, like phase
sensitivity, micro bending losses and modal noise
 Fiber endoscopes
 Using large diameter and short length silica fibers
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16. Thank You
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